Dedicated power supply apparatus, terminal, power supply system, and power supply method

ABSTRACT

A dedicated power supply apparatus includes a regulator that receives power from an external power source, two signal lines to which the regulator is connected, and two resistors, each placed between the regulator and an associated one of the two signal lines.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2005-251543 filed in the Japanese Patent Office on Aug.31, 2005, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to dedicated power supply apparatuses,terminals, power supply systems, and power supply methods, and inparticular, to a power supply technique applicable to mobile devicesthat can be carried around.

2. Description of the Related Art

A rapidly increasing number of mobile devices, such as digital audioplayers, that are small and can be carried around are being widely used.Many of these mobile devices are capable of performing high-speed datacommunication with computers by establishing universal serial bus (USB)connections. There are various methods for charging a battery in such amobile device. For example, one method uses an alternating current (AC)jack for power supply, another method uses a cradle, and yet anothermethod uses a USB. When a mobile device is provided with a USB terminalfor data communication and an AC jack for power supply, the devicebecomes larger in size and is thus not attractive in appearance, andwiring connections become complicated. There are some mobile devicesthat are provided with cradles serving as dedicated chargers for holdingand charging the mobile devices. Because it is necessary to have suchlarge cradles at all times, it is difficult to make full use of theconvenience of small mobile devices.

In view of the above-described points, it is preferable thatUSB-connectable mobile devices be charged by establishing USBconnections. When charging is done by establishing USB connections,mobile devices can be charged by simply connecting them to computers.Therefore, many mobile devices that can be charged by establishing USBconnections are not provided with an AC jack for power supply but areprovided with only a USB jack for data communication and charging inorder to reduce the size of the mobile devices, to not ruin theappearance of the mobile devices, and to enhance the simplicity ofwiring connections.

In the case of mobile devices that are not provided with AC jacks forpower supply, it is difficult to charge such a mobile device when thereis no computer. In normal usage, such a mobile device is convenientsince it can be charged by connecting it via USB to a computer. However,if a user of such a mobile device is on a trip and has no computer onhand, it is difficult to charge such a mobile device. In order toprevent this problem, adapters that can be connected to a home powersupply, convert this power to predetermined power, and supply thepredetermined power to mobile devices by establishing USB connectionshave been developed. Such adapters are referred to as “USB adapters”(for example, see Japanese Unexamined Patent Application Publication No.2005-6497).

SUMMARY OF THE INVENTION

Known USB adapters described above employ a standard four-pin USBconnector provided with a total of four terminals. The four terminalsinclude a +5 power supply terminal for power supply, a ground terminal,a D+ terminal for data transmission, and a D− terminal for datatransmission. According to the power supply specification of such USBadapters, an output voltage of 5 V±0.25 V and an output current of 500mA are necessary, and the power supply terminal is designed to satisfythe specification. In contrast, the D+ and D− terminals for datatransmission are open, and nothing has been done in this regard. Thus,the operation of the D+ and D− terminals is unstable.

When establishing a connection between a mobile device and a USBadapter, it is necessary for the mobile device not to mistakenlyrecognize that the USB adapter has been suspended. When the mobiledevice mistakenly recognizes that the USB adapter has been suspended,the mobile device can only receive power of 500 μA or less from the USBadapter. In known USB adapters, however, nothing has been done for theD+ and D− terminals for data transmission, and hence the mobile devicemay mistakenly recognize that the USB adapter has been suspended.

In view of the above-described problems, it is desirable to provide adedicated power supply apparatus, a terminal, a power supply system, anda power supply method capable of providing a safe charging system andsuppressing malfunction or unstable operation of the terminal while thededicated power supply apparatus is being connected.

According to an embodiment of the present invention, there is provided adedicated power supply apparatus for supplying power to a rechargeablepower source or the like in a mobile device. The dedicated power supplyapparatus includes a regulator that receives power from an externalpower source, two signal lines to which the regulator is connected, andtwo resistors, each placed between the regulator and an associated oneof the signal lines.

With this structure, the two signal lines can be pulled up to apredetermined voltage by placing each of the two resistors between theregulator and an associated one of the two signal lines. Accordingly, adevice connected to the dedicated power supply apparatus is preventedfrom mistakenly recognizing that the dedicated power supply apparatushas been suspended, and this device is thereby prevented from beingsuspended. Thus, malfunction or unstable operation of the device can besuppressed, and a safe charging system can be provided.

Each of the two resistors may not necessarily be placed between theregulator and an associated one of the two signal lines. For example,there are some cases where a resistor is placed between the regulatorand at least one of the signal lines. That is, there are two types ofUSB devices. One is low-speed devices, such as a mouse, and the other isfull-speed devices, such as a hard disk. By connecting the two resistorsto the associated two signal lines, both types of USB devices can behandled. In order to handle only one type of USB device, such aslow-speed devices or full-speed devices, a resistor may be connected toonly one signal line. This point will be described subsequently.

According to another embodiment of the present invention, there isprovided a terminal including a rechargeable power source or the likeand receiving power from an external device. The terminal includes aconnection portion to be connected to an external device, a battery thatreceives power from the external device via the connection portion, adetector that detects a data signal from the external device when theconnection portion is connected to the external device, a determinationunit that determines whether the external device is a dedicated powersupply apparatus on the basis of a detection result obtained by thedetector, and a controller that controls charging of the battery on thebasis of a determination result obtained by the determination unit.

The data signal from the external device may be a signal indicating thatthe external device performs data communication.

The terminal may further include a current converter that converts, onthe basis of determination performed by the determination unit, theamount of charging current from a first current prior to thedetermination to a second current larger than the first current.

The terminal can perform appropriate charging by determining whether aconnection destination at the time of charging is a computer or adedicated power supply apparatus such as a USB adapter. With thisstructure, the terminal determines whether a signal, such as start offrame (SOF), indicating that data transmission is performed istransmitted. When the terminal determines that the connectiondestination is a dedicated power supply apparatus, the terminal canperform appropriate charging.

According to a further embodiment of the present invention, there isprovided a terminal including a connection portion to be connected to anexternal device, a battery that receives power from the external devicevia the connection portion, a detector that detects whether signal linesincluded in the connector are maintained at predetermined logicalstates, such as logical high states, a determination unit thatdetermines whether the external device is a dedicated power supplyapparatus on the basis of a detection result obtained by the detector,and a controller that controls charging of the battery on the basis of adetermination result obtained by the determination unit.

With this structure, appropriate charging can be performed when it isdetermined, by determining the logical states of the two signal lines,that the communication destination is a dedicated power supplyapparatus. For example, appropriate charging can be performed when it isdetermined, by determining whether both the signal lines are maintainedat logical high states, that the communication destination is adedicated power supply apparatus.

The terminal may further include a current converter that converts, onthe basis of determination performed by the determination unit, theamount of charging current from a first current prior to thedetermination to a second current larger than the first current. Thefirst and second currents are, for example, 100 mA and 500 mA,respectively. With this structure, the amount of current can beincreased subsequent to determining that the communication destinationis a dedicated power supply apparatus. For example, the amount ofcurrent can be increased from 100 mA to 500 mA.

According to still a further embodiment of the present invention, thereis provided a power supply system including a dedicated power supplyapparatus and a terminal, to which power is supplied from the dedicatedpower supply apparatus. The dedicated power supply apparatus includes aregulator that receives power from an external power source, two signallines to which the regulator is connected, and two resistors, eachplaced between the regulator and an associated one of the two signallines. The terminal includes a connection portion to be connected to anexternal device, a battery that receives power from the external devicevia the connection portion, a detector that detects data from theexternal device when the connection portion is connected to the externaldevice, a determination unit that determines whether the external deviceis the dedicated power supply apparatus on the basis of a detectionresult obtained by the detector, and a controller that controls chargingof the battery on the basis of a determination result obtained by thedetermination unit.

With this system, in the dedicated power supply apparatus, the twosignal lines can be pulled up to a predetermined voltage by placing eachof the two resistors between the regulator and an associated one of thetwo signal lines. Accordingly, a device connected to the dedicated powersupply apparatus is prevented from being suspended. The terminaldetermines whether a signal, such as SOF, indicating that datatransmission is performed is transmitted. On the basis of thedetermination result, the terminal determines whether the connectiondestination device is the dedicated power supply apparatus, such as aUSB adapter. Accordingly, the terminal can perform appropriate charging.In this manner, malfunction or unstable operation of the terminal can besuppressed, and a safe charging system can be provided.

According to yet another embodiment of the present invention, there isprovided a power supply method for supplying power to a terminal. Thepower supply method includes the steps of: detecting whether an externaldevice is connected; receiving power from a detected external device andstarting charging; detecting a data signal from the external deviceafter starting charging; and controlling the amount of power receivedfrom the external device on the basis of a result of detecting the datasignal from the external device after starting charging.

With this method, after starting charging, the terminal detects asignal, such as SOF, indicating that the external device performs datatransmission. On the basis of the detection result, the terminalcontrols charging. In this manner, malfunction or unstable operation ofthe terminal connected to a dedicated power supply apparatus can besuppressed, and a safe charging system can be provided.

According to the embodiments of the present invention, the dedicatedpower supply apparatus includes the two resistors, each placed betweenthe regulator and an associated one of the two signal lines. Thus, thetwo signal lines can be pulled up to a predetermined voltage. Also, adevice connected to the dedicated power supply apparatus is preventedfrom being suspended. The terminal determines whether a signal, such asSOF, indicating that data transmission is performed is transmitted. Theterminal can perform appropriate charging when it is determined that thecommunication destination device is the dedicated power supplyapparatus, such as a USB adapter. In this manner, malfunction orunstable operation of the terminal can be suppressed, and a safecharging system can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example of a connection state when a USBconnection is established between a USB adapter and a device;

FIG. 2A is a diagram of the overall structure of data to be transferred,including SOF;

FIG. 2B is a diagram of the frame structure of data to be transferred,including SOF;

FIG. 2C is a diagram of the transaction structure of data to betransferred;

FIG. 3 is a diagram of a verification method of verifying transitions toa suspended state;

FIG. 4 is a table of the verification results of verifying thetransitions to the suspended state;

FIG. 5 is a diagram of a power supply system according to an embodimentof the present invention;

FIG. 6 is a flowchart of a first USB adapter detection method;

FIG. 7 is a flowchart of a second USB adapter detection method;

FIG. 8 is a flowchart of a third USB adapter detection method;

FIG. 9 is a diagram of a power supply system according to anotherembodiment of the present invention; and

FIG. 10 is a flowchart of another example of a USB adapter detectionmethod.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, a dedicated power supplyapparatus, a terminal, a power supply system, and a power supply methodaccording to preferred embodiments of the present invention will bedescribed in detail. In the specification and the drawings, elementsthat have substantially the same functions are denoted by the samereference numerals, and repeated descriptions thereof will be omitted.

According to an embodiment of the present invention, a dedicated powersupply apparatus for charging a battery that is included in a device andcan be recharged by establishing a USB connection (hereinafter referredto as a “USB adapter”) will be described. In this embodiment, the term“device” refers to a device that can receive power from a computer,which is a USB host, or from the USB adapter by establishing aconnection via USB. The device in the embodiment mainly assumes a mobiledevice that can be carried around. However, the device is not limited tothat suitable for being carried around and includes all terminals thatcan receive power from a USB-connection destination.

In this embodiment, it is desirable to prevent the device from beingsuspended while connected to the USB adapter. When the computer issuspended while the device is being connected to the computer, thedevice is also suspended. At this time, the device can only receive acurrent of about 500 μA, and it is difficult for the device to actuallyrequest the computer to supply power to the device.

When the device is connected to the USB adapter, it is not necessary tosuspend the device. However, it is difficult for the device to determinewhether a connection destination device is a USB device or a computer.Thus, the device may mistakenly recognize a state where the device isbeing connected to the USB adapter as a state where the device is beingconnected to the suspended computer. In this embodiment, it is desirableto prevent such erroneous recognition.

FIG. 1 is a diagram of an example of a power supply system. A USBadapter 110, which is an example of the dedicated power supplyapparatus, and a device 120, which is an example of the terminal, areconnected to each other via USB. The USB adapter 110 is connected via apower plug 118 to an external power source 140. FIG. 1 only showselements that are necessary for the description below.

USB Adapter 110

The USB adapter 110 includes, as shown in FIG. 1, a regulator 111, (asignal generator 112), and a USB connector 113. The regulator 111receives a voltage from the external power source 140 and converts thevoltage to a voltage that can be used as a charging voltage. Theexternal power source 140 supplies, for example, an AC voltage rangingfrom 100 V to 240 V for home power supply, and the regulator 111converts this voltage to, for example, a DC voltage of 5 V. (The signalgenerator 112 generates a signal for data transmission. It is notnecessary to provide the signal generator 112.)

The USB connector 113 is a standard four-pin USB connector and includesa +5V terminal 114, a GND terminal 115, a D+ terminal 116, and a D−terminal 117. The +5V terminal 114 and the GND terminal 115 are powersupply terminals to be connected to the regulator 111. The D+ terminal116 and the D− terminal 117 are data transmission terminals to beconnected to the signal generator 112. The D+ terminal 116 is groundedvia, for example, a resistor R12 of 15 kΩ. The D− terminal 117 isgrounded via, for example, a resistor R22 of 15 kΩ.

Device 120

The device 120 includes, as shown in FIG. 1, a USB port 121 and abattery 122. The USB port 121 is a port to which the USB connector 113of the USB adapter 110 is connected. The USB port 121 includes a Vusbterminal 123, a GND terminal 124, a D+ terminal 125, and a D− terminal126. The battery 122 is a rechargeable power source and is, for example,a lithium-ion battery.

Upon connection of the device 120 to the USB adapter 110, the Vusbterminal 123 is connected to the +5V terminal 114 of the USB adapter110, the GND terminal 124 is connected to the GND terminal 115 of theUSB adapter 110, the D+ terminal 125 is connected to the D+ terminal 116of the USB adapter 110, and the D− terminal 126 is connected to the D−terminal 117 of the USB adapter 110.

The D+ terminal 125 is connected via, for example, a resistor 31 of 1.5kΩ to a 3.3 V power source and is thereby pulled up. The device 120shown in FIG. 1 assumes a device, such as a hard disk, that performsfull-speed communication. When the device 120 is a device, such as amouse, that performs low-speed communication, the D− terminal 126 is tobe pulled up.

The device 120 recognizes a connection with the USB adapter 110 when +5V power is supplied from the +5V terminal 114 of the USB adapter 110 tothe Vusb terminal 123. In contrast, the USB adapter 110 recognizes aconnection with the device 120 when the device 120 pulls up the D+terminal 116 using the resistor 31.

The case of transition to a suspended state of a device that establishesa USB connection, such as that shown in FIG. 1, will be described. Adevice that establishes a USB connection, such as that shown in FIG. 1,determines whether a connection destination electronic device, such as acomputer, has been suspended. If it is determined that the connectiondestination electronic device has been suspended, the device is alsosuspended. When the USB-connection destination is idle for 3 ms orlonger and when no SOF or no other signals are sent from theUSB-connection destination, the device 120 is suspended. The idle stateis a state where, in the case of a low-speed device, the D+ terminal 125is low and the D− terminal 126 is high, and, in the case of a full-speeddevice, the D+ terminal 125 is high and the D− terminal 126 is low. Inthis specification, the logical high state is simply expressed as“high”, and the logical low state is simply expressed as “low”.

The SOF will now be described. FIGS. 2A to 2C are diagrams of thestructure of data to be transferred, including SOF. The actual dataflowing on a USB line is communicated in units referred to as “frames”.A frame is repeatedly transferred with a 1 ms period, as shown in FIG.2A. All data is exchanged in frames. The frame structure includes, asshown in FIG. 2B, a plurality of “transactions” starting with a “packet”referred to as a “start of frame (SOF)”. A packet is a minimum unitcommunicated in USB communication, and there are a few types of packets.When a few packets are communicated to form a unit of meaningful datatransmission, this unit is referred to as a “transaction”. As shown inFIG. 2C, there are three types of transactions including SETUP, OUT, andIN. The length of data to be transferred depends on the setting.

As has been described above, by preventing the USB adapter 110 frombeing idle while the device 120 is being USB-connected to the USBadapter 110, it can be regarded that it is possible to prevent thedevice 120 from being suspended. As shown in FIG. 3, in a USB adapter210, it is assumed that resistors R11 and R12 of 15 kΩ are connected toa D+ terminal 211, and resistors R21 and R22 of 15 kΩ are connected to aD− terminal 212. The resistors R11, R12, R21, and R22 are connected anddisconnected to verify whether the device 220 becomes suspended.

FIG. 4 is a table of the results of verification performed in FIG. 3.Which resistors are connected to the D+ terminal 211 and the D− terminal212 is determined by various viewpoints, such as preventing the USBadapter 210 from being suspended, preventing the D+ terminal 211 and theD− terminal 212 from presenting high impedance, and preventingunnecessary leakage current. In the states of the D+ terminal 211 andthe D− terminal 212 indicated by rows A, B, C, D, and E of the tableshown in FIG. 4, it is difficult to prevent the D+ terminal 211 and theD− terminal 212 from presenting high impedance. In the states of the D+terminal 211 and the D− terminal 212 indicated by rows G, H, and I, thedevice 220 mistakenly recognizes that the USB adapter 210 is idle. It isthus difficult to prevent the device 220 from being suspended. Forexample, row H indicates the case where the D+ terminal 211 is low andthe D− terminal 212 is high. In this case, the device 220 mistakenlydetermines that the connection destination USB adapter 210 is alow-speed device and is idle. However, in the states of the D+ terminal211 and the D− terminal 212 indicated by row F, the D+ terminal 211 andthe D− terminal 212 do not present high impedance, and the device 220 isnot suspended. Therefore, it has been verified that it is optimal toconnect the resistors R11 and R12 to the D+ terminal 211 and the D−terminal 212, respectively, to pull up both the D+ terminal 211 and theD− terminal 212. The pull-up voltage is, for example, 3.3 V. By pullingup both the D+ terminal 211 and the D− terminal 212, the device 220connected to the USB adapter 210 is prevented from being suspended.

FIG. 5 is a diagram of a power supply system according to an embodimentof the present invention and shows a USB connection between a USBadapter 310, which is an example of the dedicated power supplyapparatus, and a device 320, which is an example of the terminal. TheUSB adapter 310 is connected via a power plug 319 to an external powersource 340. FIG. 5 only shows elements that are necessary for thedescription below.

USB Adapter 310

The USB adapter 310 includes, as shown in FIG. 5, a regulator 311 and aUSB connector 313. The regulator 311 receives a voltage from theexternal power source 340 and converts the voltage to a voltage that canbe used as a charging voltage. The external power source 340 supplies,for example, an AC voltage ranging from 100 V to 240 V for home powersupply, and the regulator 311 converts this voltage to, for example, aDC voltage of 5 V.

The USB connector 313 is a standard four-pin USB connector and includesa +5V terminal 314, a GND terminal 315, a D+ terminal 316, and a D−terminal 317. The +5V terminal 314 and the GND terminal 315 are powersupply terminals to be connected to the regulator 311. The D+ terminal316 and the D− terminal 317 are data transmission terminals, which willbe described subsequently.

The USB adapter 310 shown in FIG. 5 is different from the USB adapter110 shown in FIG. 1 in that, for example, the D+ terminal 316 isconnected to a regulator 318 via, for example, the resistor R11 of 15kΩ, and the D− terminal 317 is connected to the regulator 318 via, forexample, the resistor R21 of 15 kΩ. The regulator 318 receives a voltagefrom the +5 terminal 314 and the GND terminal 315, which are powersupply terminals, and converts this voltage to, for example, 3.3 V.Thus, the D+ terminal 316 and the D− terminal 317, which are datatransmission terminals, can be pulled up to 3.3 V. The USB adapter 310includes no signal generator 112 shown in FIG. 1, and the resistors R11and R12 are connected to the D+ terminal 316 and the 317, respectively.

In this embodiment, the case where the D+ terminal 316 and the D−terminal 317 are pulled up to 3.3 V is described by way of example.However, the present invention is not limited to this case.Alternatively, the D+ terminal 316 and the D− terminal 317 may be pulledup to an arbitrary voltage, such as 1.5 V or 15 V.

In this embodiment, the case where both the D+ terminal 316 and the D−terminal 317 are pulled up is described by way of example. However, thepresent invention is not limited to this case. Alternatively, alow-speed device can be handled by pulling up the D+ terminal 316 of theUSB adapter 310, and a full-speed device can be handled by pulling upthe D− terminal 317 of the USB adapter 310. At present, most USB devicesare full-speed devices, and it is expected that this trend will continuein the future. In the case where a full-speed device is to be handledand no low-speed device is taken into consideration, only the D−terminal 317 of the USB adapter 310 may be pulled up.

As has been described above, according to the USB adapter 310 accordingto the embodiment, the D+ terminal 316 and the D− terminal 317 of theUSB adapter 310 are pulled up. Thus, the device 320 is prevented frombeing suspended, which may be caused by the device 320 mistakenlyrecognizing that the USB adapter 310 has been suspended.

Next, the device will be described. The structure of the device 120shown in FIG. 1 does not enable the device 120 to determine whether theUSB connection destination is a computer or a USB adapter. Basically,the USB standard does not allow the current supply to the device 120 tobe increased from 100 mA to 500 mA unless permission is obtained from acomputer serving as the connection destination. However, when theconnection destination is a USB adapter, it is not necessary for thedevice 120 to obtain permission from the USB adapter. Thus, when it isnecessary to quickly charge the device 120 by receiving a current of 500mA, it is necessary for the device 120 to detect whether the USBconnection destination is a USB adapter or a computer. Hereinafter, howthis point can be accomplished will be described.

It is only necessary for the device 320 to determine whether the USBconnection destination is a computer or a USB adapter. When the USBconnection destination is a computer, the device 320 can receive acurrent of 500 mA after obtaining permission from the computer. When theUSB connection destination is a USB adapter, the device 320 can receivea current of 500 mA without obtaining permission from the USB adapter.Hereinafter, the structure of the device based on this viewpoint will bedescribed.

Device 320

The device 320 includes, as shown in FIG. 5, a USB port 321 and abattery 322. The USB port 321 is a port to which the USB connector 313of the USB adapter 310 is connected. The USB port 321 includes a Vusbterminal 323, a GND terminal 324, a D+ terminal 325, and a D− terminal326. The battery 322 is a rechargeable power source and is, for example,a lithium-ion battery.

Upon connection of the device 320 to the USB adapter 310, the Vusbterminal 323 is connected to the +5V terminal 314 of the USB adapter310, the GND terminal 324 is connected to the GND terminal 315 of theUSB adapter 310, the D+ terminal 325 is connected to the D+ terminal 316of the USB adapter 310, and the D− terminal 326 is connected to the D−terminal 317 of the USB adapter 310.

The D+ terminal 325 is connected via, for example, the resistor 31 of1.5 kΩ to the 3.3 V power source and is thereby pulled up. The device320 shown in FIG. 5 assumes a full-speed device, such as a hard disk.When the device 320 is a low-speed device, such as a mouse, the D−terminal 326 is to be pulled up.

The device 320 recognizes a connection with the USB adapter 310 when +5V power is supplied from the +5V terminal 314 of the USB adapter 310 tothe Vusb terminal 323. In contrast, the USB adapter 310 recognizes aconnection with the device 320 when the device 320 pulls up the D+terminal 316 using the resistor 31.

The device 320 shown in FIG. 5 further includes a detector 327, adetermination unit 328, a controller 329, a playback controller 330, aplayback unit 331, a storage medium 332, and an operation unit 333. Thedetector 327 is connected to the D+ terminal 325 and the D− terminal 326for data transmission. When the USB port 321 is connected to an externaldevice such as the USB adapter 310 or a computer, the detector 327detects a signal indicating that the external device performs datatransmission. The determination unit 328 is connected to the detector327 and determines whether the external device is the USB adapter 310 onthe basis of the detection result obtained by the detector 327.

The controller 329 is connected to the determination unit 328, the Vusbterminal 323 and the GND terminal 324 for power supply, and the battery322. The controller 329 controls the charging of the battery 322 on thebasis of the determination result obtained by the determination unit328.

The playback controller 330 receives a command from the operation unit333 and controls the playback unit 331. The playback unit 331 plays backan audio file, such as an MP3 file, stored on the storage medium 332.Also, the playback unit 331 may be capable of playing back, in additionto audio files, files including images, moving images, and text. Anoutput unit 335 outputs the audio file or the like played back by theplayback unit 331. The output unit 335 may be placed inside or outsidethe device 320.

The detector 327, the determination unit 328, the controller 329, theplayback controller 330, and the playback unit 331 may be implemented asfunctions of a central processing unit (CPU) 334. Each function of theCPU 334 mainly consumes power charged in the battery 322 when executingprocessing.

There are three methods of the detector 327 of the device 320determining whether the USB connection destination is a computer or aUSB adapter, which will be described subsequently.

(1) SOF Signal Detection

When a device connected via USB to the device is a computer, thecomputer sends SOF to the device once in every predetermined period oftime. The predetermined period of time is, for example, 1 ms. Incontrast, because the USB adapter will not be in a suspended mode, theUSB adapter sends no SOF to the device. Thus, when no SOF is sent fromthe USB connection destination within the predetermined period of timeor longer, the device can determine that the connection destination is aUSB adapter.

The flow of USB adapter detection will now be described with referenceto FIG. 6. The USB connection destination will be referred to as the“external device”, which is, for example, a USB adapter or a computer.

In step S102, the device 320 is connected to the external device. Instep S104, the device 320 recognizes a connection with the externaldevice when the external device supplies +5 power to the Vusb terminal323. In step S106, the device 320 starts charging at 100 mA. In stepS108, the device 320 starts an SOF queue timer. In step S110, the device320 determines whether SOF is detected within the predetermined periodof time.

If no SOF was detected and time ran out in step S110, in step S112, thedevice 320 recognizes that the USB connection destination is a USBadapter and starts charging at 500 mA. In step S114, after startingcharging at 500 mA, the device 320 again determines whether SOF isdetected within the predetermined period of time. If SOF is detected, instep S116, the device 320 determines that there was a mistake inrecognition of the USB connection destination, and the device 320returns to charging at 100 mA.

If SOF is detected in step S110, in step S118, the device 320 recognizesthat the USB connection destination is a computer. The device 320 stopsthe SOF timer upon reception of even one command from the computer. Instep S120, the computer executes the “Chapter 9 Protocol” handling torecognize a terminal connected thereto. In step S122, the device 320sets whether to receive a current of 100 mA or a current of 500 mA afterobtaining permission from the computer. In step S124, the device 320performs the normal USB processing.

(2) Signal Line D+/D− Logical State Detection

A second method of the detector 327 of the device 320 determiningwhether the USB connection destination is a computer or a USB adapterwill now be described.

According to the second method, the detector 327 of the device 320,which is connected to the D+ terminal 325 and the D− terminal 326 fordata transmission, has a function of determining whether the signallines D+ and D− are maintained at predetermined logical states. Theremaining portions are the same as those shown in FIG. 5.

The flow of USB adapter detection will now be described with referenceto FIG. 7.

In step S202, the device 320 is connected to the external device. Instep S204, the device 320 recognizes a connection with the externaldevice when the external device supplies +5 power to the Vusb terminal323. In step S206, the device 320 starts charging at 100 mA.

In step S208, the device 320 detects the states of the signal lines D+and D− using the detector 327. The device 320 determines whether thesignal lines D+ and D− are maintained at high/high states on the basisof the detection result.

If it is determined in step S208 that the signal lines D+ and D− aremaintained at high/high states, in step S210, the device 320 recognizesthat the USB connection destination is a USB adapter and starts chargingat 500 mA.

In contrast, if it is determined in step S208 that the signal lines D+and D− are not maintained at high/high states, in step S212, the device320 recognizes that the USB connection destination is a computer. Thecomputer executes the “Chapter 9 Protocol” handling to recognize aterminal connected thereto. In step S214, the device 320 sets whether toreceive a current of 100 mA or a current of 500 mA after obtainingpermission from the computer. In step S216, the device 320 performs thenormal USB processing.

(3) SOF Signal Detection and D+/D− Logical State Detection

A third method of the detector 327 of the device 320 determining whetherthe USB connection destination is a computer or a USB adapter will nowbe described.

According to the third method, the detector 327 of the device 320, whichis connected to the D+ terminal 325 and the D− terminal 326 for datatransmission, has two functions. One is to detect an SOF signal, and theother is to determine whether the signal lines D+ and D− are maintainedat predetermined logical states. The remaining portions are the same asthose shown in FIG. 5.

The flow of USB adapter detection will now be described with referenceto FIG. 8.

In step S302, the device 320 is connected to the external device. Instep S304, the device 320 recognizes a connection with the externaldevice when the external device supplies +5 power to the Vusb terminal323. In step S306, the device 320 starts charging at 100 mA.

In step S308, the device 320 starts the SOF queue timer. In step S310,the device 320 determines whether SOF is detected within thepredetermined period of time. In addition, the device 320 detects thestates of the signal lines D+ and D− and determines whether the signallines D+ and D− are maintained at high/high states.

If it is determined in step S310 that the signal lines D+ and D− aremaintained at high/high states, in step S312, the device 320 recognizesthat the USB connection destination is a USB adapter and starts chargingat 500 mA. In step S314, after starting charging at 500 mA, the device320 again determines whether SOF is detected within the predeterminedperiod of time. If SOF is detected, in step S316, the device 320determines that there was a mistake in recognition of the USB connectiondestination, and the device 320 returns to charging at 100 mA.

If SOF is detected in step S310, in step S318, the device 320 recognizesthat the USB connection destination is a computer. The device 320 stopsthe SOF timer upon reception of even one command from the computer. Instep S320, the computer executes the “Chapter 9 Protocol” handling torecognize a terminal connected thereto. In step S322, the device 320sets whether to receive a current of 100 mA or a current of 500 mA afterobtaining permission from the computer. In step S324, the device 320performs the normal USB processing.

According to the third method, the device performs both the SOF signaldetection and the D+/D− logical state detection. It thus becomesunnecessary for the device to continue detecting SOF until the time ofthe SOF timer runs out. In this manner, the period of time fordetermining whether the USB connection destination is a computer or aUSB adapter can be reduced.

As has been described above, the device 320 according to this embodimentincludes the detector 327, the determination unit 328, and thecontroller 329. The device 320 can determine whether the USB connectiondestination is a computer or a USB adapter. Thus, even when it isnecessary to quickly charge the device 320, optimal charging can beperformed.

The case where the device 320 mistakenly detects a USB adapter when anyone of the methods according to this embodiment is used will now bedescribed. When the device 320 mistakenly detects that the USBconnection destination is a USB adapter, the device 320 changes thecurrent limit from 100 mA to 500 mA. When the USB connection destinationis capable of supplying a current of 500 mA or greater, no significantproblems will be caused. For example, when the USB connectiondestination is a root hub, the root hub is capable of supplying acurrent of 500 mA or greater. However, when the USB connectiondestination is a bus-powered hub, the bus-powered hub is capable of onlysupplying a current of 100 mA. As long as power is supplied to thebus-powered hub, the bus-powered hub outputs SOF regardless of the hoststate. Thus, the device will not mistakenly detect a USB adapter. Evenwhen the device mistakenly detects a USB adapter, no significantnegative impact will be caused.

Although the dedicated power supply apparatus, the terminal, the powersupply system, and the power supply method according to the preferredembodiment of the present invention have been described with referenceto the accompanying drawings, the present invention is not limitedthereto. It is anticipated by those skilled in the art that a variety ofmodifications or changes may be made without departing from thetechnical scope of the invention set forth in the appended claims, andthese modifications or changes may also be embraced in the scope of thepresent invention.

For example, in the above-described embodiment, the USB adapter, whichincludes no signal generator but includes the D+ terminal 316 and the D−terminal 317 connected to the resistors R11 and R21, has been described.However, the present invention is not limited thereto. For example, asshown in FIG. 9, a signal generator 312 for generating a signal for datatransmission may be provided.

In “(3) SOS Signal Detection and Signal Line D+/D− Logical StateDetection” in the above-described embodiment, the case where the SOSsignal detection and the D+/D− logical state detection are performed inparallel with each other has been described. However, the presentinvention is not limited to this case. For example, a process shown inFIG. 10 may be performed.

In the example shown in FIG. 10, steps S302, S304, S306, S308, S312,S314, S316, S318, S320, S322, and S324 are such as those describedabove. Steps S309 and S311 will now be described. In step S309, thedevice 320 determines whether SOF is detected within the predeterminedperiod of time. If SOF is detected, the device 320 determines that theUSB connection destination is a computer. When no SOF was detected andtime ran out, in step S311, the device 320 further detects the states ofthe signal lines D+ and D− and determines whether the logical states ofthe signal lines D+ and D− are maintained at high/high states. If thelogical states of the signal lines D+ and D− are maintained at high/highstates, the device 320 determines that the device connected thereto viaUSB is a USB adapter. If the logical states of the signal lines D+ andD− are not maintained at high/high states, the device 320 determinesthat the device connected thereto via USB is a computer.

The SOF detection in step S309 and the high/high state detection in stepS311 may be performed in the opposite order. Also, the series ofprocesses may be performed by hardware by implementing the functionalblocks shown in FIGS. 5 and 9 using hardware.

Accordingly, the present invention can be employed in a dedicated powersupply apparatus, a terminal, a power supply system, and a power supplymethod. In particular, the present invention can be employed in adedicated power supply apparatus, a terminal, a power supply system, anda power supply method applicable to a mobile device that can be carriedaround, such as an audio player, a mobile phone, a digital camera, acamcorder, a portable game console, or a notebook computer. Also, thepresent invention is applicable to a dedicated power supply apparatus, aterminal, a power supply system, and a power supply method using notonly a USB connector but also any type of connector for both datatransmission and power supply.

1. A dedicated power supply apparatus comprising: a regulator thatreceives power from an external power source; two signal lines to whichthe regulator is connected; and two resistors, each placed between theregulator and an associated one of the two signal lines.
 2. A terminalcomprising: a connection portion to be connected to an external device;a battery that receives power from the external device via theconnection portion; a detector that detects a data signal from theexternal device when the connection portion is connected to the externaldevice; a determination unit that determines whether the external deviceis a dedicated power supply apparatus on the basis of a detection resultobtained by the detector; and a controller that controls charging of thebattery on the basis of a determination result obtained by thedetermination unit.
 3. The terminal according to claim 2, wherein thedata signal from the external device is a signal indicating that theexternal device performs data communication.
 4. The terminal accordingto claim 3, further comprising a current converter that converts, on thebasis of determination performed by the determination unit, the amountof charging current from a first current prior to the determination to asecond current larger than the first current.
 5. A terminal comprising:a connection portion to be connected to an external device; a batterythat receives power from the external device via the connection portion;a detector that detects whether signal lines included in the connectorare maintained at predetermined logical states; a determination unitthat determines whether the external device is a dedicated power supplyapparatus on the basis of a detection result obtained by the detector;and a controller that controls charging of the battery on the basis of adetermination result obtained by the determination unit.
 6. The terminalaccording to claim 5, further comprising a current converter thatconverts, on the basis of determination performed by the determinationunit, the amount of charging current from a first current prior to thedetermination to a second current larger than the first current.
 7. Apower supply system comprising: a dedicated power supply apparatus; anda terminal, to which power is supplied from the dedicated power supplyapparatus, wherein the dedicated power supply apparatus includes aregulator that receives power from an external power source, two signallines to which the regulator is connected, and two resistors, eachplaced between the regulator and an associated one of the signal lines,and wherein the terminal includes a connection portion to be connectedto an external device, a battery that receives power from the externaldevice via the connection portion, a detector that detects data from theexternal device when the connection portion is connected to the externaldevice, a determination unit that determines whether the external deviceis the dedicated power supply apparatus on the basis of a detectionresult obtained by the detector, and a controller that controls chargingof the battery on the basis of a determination result obtained by thedetermination unit.
 8. A power supply method comprising the steps of:detecting whether an external device is connected; receiving power froma detected external device and starting charging; detecting a datasignal from the external device after starting charging; and controllingthe amount of power received from the external device on the basis of aresult of detecting the data signal from the external device afterstarting charging.
 9. A terminal comprising: connection means for beingconnected to an external device; battery means for receiving power fromthe external device via the connection means; detecting means fordetecting a data signal from the external device when the connectionmeans is connected to the external device; determining means fordetermining whether the external device is a dedicated power supplyapparatus on the basis of a detection result obtained by the detectingmeans; and control means for controlling charging of the battery on thebasis of a determination result obtained by the determining means.